A rotary potentiometer of that type that has a driving member is used, for example, in an electronic carburetor of a motor vehicle (cf. Krafthand, Vol. 15, Aug. 6, 1983, p. 877 to 881). In such application, the control of the mixture concentration during starting, running up and acceleration is effected electronically. The air/fuel ratio is influenced by means of a throttle valve. A throttle valve rotary potentiometer serves for determining the position and the sequence of motion of the throttle valve, which throttle valve potentiometer is connected with the throttle shaft by means of a coupling.
In W. German patent application No. P 34 44 229.4 and U.S. Pat. No. 4,701,740, a rotary potentiometer of the above type is described. In this case, the rotary body, i.e., the body being driven to rotate, has a depression, at the inner edge of which two teeth offset by 180.degree. are provided, the crests of which teeth are directed to the rotary axis. The flanks of the teeth, which are designed to be engaged by a drive means when the body is to be turned, are flat-shaped, i.e., they present flat surfaces to the drive member which engages them. This arrangement is disadvantageous because some slight axle misalignment between the rotary body and the driving means is unavoidable, in which case different torque ratios may result. This results in the force being necessary for driving the rotary body of revolution to vary.